The ring of immunity carries more DV and PV bonuses than any other ring in the game, and completely eliminates all elemental damage both from temples (i.e. Tower of Eternal Flames and the Air Temple) and magic/breath attacks. These qualities make the ring one of the best rings, if not one of the best artifacts, in the game. The fact that it grants all elemental immunities from a single item also leaves more options open to the PC when equipping for battles (as they won't need to wear dragon scale mails or elemental crowns, for example).

What the ring does lack, however, is some other useful intrinsics like paralyzation resistance — meaning that some PCs that are already well protected against the elements might prefer to find an artifact like Preserver in a surge of power.

-----------------------------------sapphire ring--------------------------------
The sapphire ring is actually a blessed ring of immunity [+5, +5].
It is an artifact.
When worn it modifies DV by +5 and PV by +5.
When used in melee combat it grants a +0 bonus to hit and causes 1d1 points of
damage. When used as a missile it grants a +0 bonus to hit and causes 1d1
points of damage.
It grants immunity to fire.
It grants immunity to cold attacks.
It grants immunity to shock attacks.
It grants immunity to acid.